This invention relates to a method for melt nitriding of aluminum or its alloy capable of greatly increasing the wear resistance thereof.
When aluminum or its alloy is used for members adapted to move in sliding movement, it has hitherto been common practice to subject the aluminum-containing material to a suitable surface treatment, such as plating, anodic oxidation, etc., to increase its wear resistance, depending on the circumstances or conditions under which the specific sliding movement operates. When such surface treatment is carried out, a time-consuming operation must be performed because pre-treatment and after-treatment must be performed before and after the surface treatment, and special caution should be exercised in disposing of waste liquid. As a result, such surface treatment of the prior art has had the disadvantage of increasing the cost of products.
Also, aluminum or its alloy has strong affinity with oxygen in the air and readily combines therewith to form a dense layer of alumina (Al.sub.2 O.sub.3) of very small thickness. The existance of this alumina layer interferes with any surface treatment that might be applied to the material. Because of this, there has been almost no established method available for nitriding of aluminum or its alloy.